Cr(VI) induces DNA damage, cell cycle arrest and polyploidization: a flow cytometric and comet assay study in Pisum sativum

Chromium(VI) is recognized as the most toxic valency of Cr, but its genotoxicity and cytostaticity in plants is still poorly studied. In order to analyze Cr(VI) cyto- and gentotoxicity, Pisum sativum L. plants were grown in soil and wateredwithsolutionswithdifferentconcentrationsofCrupto 2000 mg/L. After 28 days of exposure, leaves showed no significant variations in either cell cycle dynamics or ploidy level. As for DNA damage, flow cytometric (FCM) histograms showed significant differences in full peak coefficient of variation(FPCV)values,suggestingclastogenicity.Thisisparalleled bytheCometassayresults,showinganincreaseinDNAdamagefor1000and2000mg/L.Inroots,exposureto2000mg/Lresulted in cell cycle arrest at the G2/M checkpoint. It was also verified that under the same conditions 40% of the individuals analyzed suffered polyploidization having both 2C and 4C levels. DNA damage analysis by the Comet assay and FCM revealed dosedependentincreasesinDNAdamageandFPCV.Throughthis,wehaveunequivocallydemonstratedforthe firsttimeinplantsthat Cr exposure can result in DNA damage, cell cycle arrest, and polyploidization. Moreover, we critically compare the validity of the CometassayandFCMinevaluatingcytogenetictoxicitytestsinplantsanddemonstratethatthedataprovidedbybothtechniques complementeachother andpresenthighcorrelationlevels.Inconclusion,thedatapresentedprovides newinsightonCreffectsin plants in general and supports the use of the parameters tested in this study as reliable endpoints for this metal toxicity in plants.We thank Eng. Armando Costa for technical assistance and Professor Elsa Vilela Filipe for revising the manuscript.publishe